Cylindrical filter panel screen for a water intake

ABSTRACT

A device for filtering a stream of water in a channel ( 2 ), includes:
         a wall ( 6 ) adapted to be mounted in the channel and including a through-opening,   a filter member ( 10 ) mounted on the wall opposite the through-opening and including a filter surface projecting relative to the wall, the filter surface having a larger area than would have a flat filter surface fitted in the through-opening, the filter member including retaining members face to face with the filter surface for retaining the bodies that do not pass through the surface,   a suction device disposed facing the retaining members, and   elements for driving the filter member and/or the suction device in a relative movement of one in relation to the other such that the suction device is successively brought face to face with each retaining member.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to filtration devices such as for examplefilter panel screens equipping water intakes, whether they be waterintakes in rivers or in the sea, to stop debris and particles conveyedby the water to extract.

Description of the Related Art

Generally, a screen for a water intake is normally disposed downstreamof a grating of bars which are spaced apart by a few centimetersprotecting the screen from debris of large size, either in isolation, orin association with one or more other screens of the same type belongingto the same screening station.

In known manner, the filter member, of which the mesh openings are onlya few millimeters across, is generally movable in order to beperiodically cleared of debris and particles which, having dimensionsgreater than those of the mesh openings, progressively obstruct all ofthem and thus clog the filter member.

Such a movable filter member may be constituted by a panel which can beraised in its own plane, alternating with another panel of the same typedisposed parallel to the preceding one, at a distance therefrom.

Such a filter member may also be constituted by an endless loop, ofelongate cross-section, for the constitution of a filter band, alsoreferred to as a thru-flow or dual flow band screen.

Such a filter member may also be constituted by an endless loop, ofcylindrical or polygonal cross-section, for the constitution of a drumscreen.

Whatever the case, such a movable filter member for a water intake,whether it be a filter panel screen, a filter band or a drum screen,passes cyclically from an immersion position in which it becomesprogressively loaded with debris and various particles, to anon-immersion position. In the latter position, it is subjected to theeffects of water jets under pressure acting in a counter-flow directionto rid it of particles and debris so applied to its surface and tothereby make it suitable once again to assume its filtration functionduring its later immersion.

The particles and debris thus taken by the washing water are typicallycollected collectively, in a trough provided for that purpose and areremoved to a drain by it.

If fish are present on the panels, they are thus removed from the waterand subjected to impacts which most often kill them.

Similarly, certain leakages may occur between the panels themselves, orbetween them and the fixed lateral uprights of the filter frame.

Furthermore, the fish that are trapped or carried away by the movablefilter member of a screen at such a water intake, are irremediablysubjected to:

-   -   a passage, often prolonged, out of the water, during the phase        of non-immersion of that filter member,    -   the action of the washing water jets applied to it, which is        most often brutal and    -   the violent projection resulting therefrom, into the trough        provided for the retrieval of all the particles and debris that        had temporarily clogged the filter member in question.

Thru-flow band screens, that is to say filter bands for which only theupstream face of the filter apron receives the water to filter, alsohave various drawbacks, which are the following:

First of all, at the bottom of the sluice, it is necessary to provide,at the base of the filter apron, for sealing between it and said base, asealing plate, referred to as foot plate, which must be tangential tosaid apron.

However, given the inevitable tolerances for manufacturing, for assemblyand for wear of the parts and, in particular, of that of theapron-carrying chains, a minimum clearance always remains between such afoot plate and the filter apron and, in practice, this clearance isnever less than approximately 6 mm, and even frequently exceeds thisvalue.

It follows that, in order to be consistent, the filter aprons of suchthru-flow band screens cannot be equipped with mesh openings less than 6mm across, and that the efficacy of treatment provided is therebylimited accordingly.

As concerns dual flow band screens, the filter apron has generatricesparallel to the direction of flow of the water stream to filter.

Both faces of this filter apron have, in parallel, identical roles,either with said stream flowing from the outside to the inside of thefilter apron through each of the faces thereof, or with it flowing inthe opposite direction.

The frame bearing such dual flow band screens is usually disposedagainst small masonry walls, one facing the other in the sluice to beequipped.

With no sealing needing to be provided at the foot of their apron, suchdual flow band screens have the advantage of enabling the utilizationfor that screen of smaller mesh openings, for example less than 0.5 mm,without inconsistency with any other sealing.

They also have the advantage of enabling simultaneous use of both facesof their apron and thus of doubling, for the same volume, the effectivefiltration area, that is to say the capacity of the equipment.

Nevertheless, dual flow band screens give no improvement in the survivalof fish relative to thru-flow band screens.

Admittedly, various devices have already been proposed for equipping awater intake screening station, for the purpose of ensuring theprotection of living components and, in particular, fish, conveyed bythe water to extract. However, in the embodiments of this type known todate, this has concerned either special filters, not in themselvesensuring the protection of the fish without any general screeningfunction at all, or conventional screening filters obliging a passageout of water for the fish collected.

BRIEF SUMMARY OF THE INVENTION

The present invention thus generally relates to enabling filtration orscreening to be provided, in particular for a water intake, while nothaving the drawbacks of the prior structures, and, where applicable,also enabling fish to be protected.

Furthermore, for the installation currently equipped with thru-flow bandscreens, the problem is increasingly arising of improving the efficacyof screening by reducing the dimensions of the debris or organisms thatcan be retained.

However, to date, their substitution by apparatus providing at least thesame function, without having the drawbacks thereof and withoutmodification of the construction works or hydraulic disturbance, cannoteasily be achieved either, as the physical conditions for theirimplementation are different.

The filter panel screen of the French patent filed under the number0406776 fully solves this problem. It is however limited in capacitywhen required to treat a high flow or to screen very finely. In boththese cases, the head loss of the screen increases. In order to solvethese difficulties, the present invention enables the area of the filtersurface presented to the fluid to be increased while retaining theoperating principles of the screen of the aforementioned patent.

The present invention thus relates to a filter device or filter memberscreen with a large filtration surface.

According to a first aspect, the invention concerns a device forfiltering a stream of water in a channel, characterized in that thedevice comprises:

-   -   a frame-forming wall adapted to be mounted in the channel and        which comprises a through-opening,    -   a filter member mounted on the frame-forming wall opposite the        through-opening and which comprises a filter surface projecting        relative to the wall, the filter surface having a larger area        than would have a flat filter surface fitted in the        through-opening, the filter member comprising retaining members        provided face to face with the filter surface in order to retain        the solid bodies that do not pass through the filter surface,    -   at least one suction device which is disposed facing the        retaining members,    -   means for driving the filter member and/or said at least one        suction device in a relative movement of one in relation to the        other such that said at least one suction device is successively        brought face to face with each retaining member.

Such a device has a filtration surface of much greater area than thecircular filter surface of the screen of the aforementioned prior art,which enables a higher water flow to be treated.

To be precise, the filter surface according to the invention extendsfrom the frame-forming wall, forming a three-dimensional surface (asurface that is not flat) instead of the two-dimensional surface of theprior art.

According to a possible feature, the filter surface is cylindrical,which in a particularly simple manner considerably increases the size ofthe filter surface of the prior art. The height of the cylindricalsurface which corresponds to the dimension in which it extends from theframe-forming wall or the diameter of the cylindrical surface may bemodified according to the filtering/screening capacity it is wished togive the device.

If the height of the cylindrical surface becomes too great relative tothe diameter of the cylinder, bending forces are thus created at thefoot of the axis fastened to the wall. In these circumstances a supportfor the free end of the surface may be necessary in order to avoiddeformations thereof under the effect of its weight.

According to a possible feature, the axis of revolution of thecylindrical filter surface is disposed perpendicularly to thethrough-opening of the frame-forming wall.

This configuration is particularly simple. The cylindrical filtersurface is positioned in front of the opening of the wall and is open atits end that faces the opening in order for the water to pass throughthe filter member, enter inside the filter cylinder and escape by theopening in the downstream direction relative to the wall.

An opposite flow of the water may also be envisaged. It should be notedthat in this case the retaining members are disposed inside thecylindrical filter surface and not outside.

In the configuration presented above the free end of the filter surfaceis closed in order to force the flow of water through the cylindricalfilter surface. According to a possible feature, the retaining membersare disposed parallel to each other along generatrices of thecylindrical filter surface.

These members thereby form longitudinal compartments at the outerperiphery of the cylindrical filter surface.

This arrangement of compartments is particularly simple to produce andeffective.

According to a possible feature, the aforementioned retaining membersare formed by two partitions spaced apart parallel to each other,arranged along generatrices of the cylindrical filter surface.

These longitudinal partitions are generally distributed around thefilter surface.

According to another possible embodiment, the filter surface is conicaland not cylindrical as described above.

In this configuration, the base of the cone is in contact with theframe-forming wall and the conical filter surface extends away from thewall, substantially perpendicularly thereto towards the point of thecone.

It should be noted that the filter surface may alternatively befrusto-conical. The retaining members arranged on the periphery of theconical filter surface are then disposed along generatrices of the coneand thereby, in a plan view, form compartments of triangular generalshape, the point of the triangle being directed towards the point of thecone.

Here too, the increase in the area of the filter surface resulting fromsuch a shape enables a higher flow of water to be treated/screened thanthe circular filter surface of the screen of the prior art dealt withabove.

It should be noted that when a conical or frusto-conical filter surfaceis used with an opposite water flow, that is to say that the water firstof all passes through the opening in the frame-forming wall, then entersinside the filter surface and passes therethrough to come out againdownstream thereof on the other side of the filtration device, theretaining members are disposed within the conical surface and notoutside.

According to another possible feature, the filter member is movablewhereas said at least one suction device is fixed.

According to another possible alternative feature, the filter member isfixed whereas said at least one suction device is movable.

According to another possible alternative feature, the filter member andsaid at least one suction device are movable.

It should be noted that, whatever the embodiment presented above, arelative movement must be established between the filter member(whatever the form of the filter surface) and the suction device ordevices in order for the latter device or devices to be broughtsuccessively face to face with each retaining member to suck away thevarious solid bodies stopped by the filter surface.

According to a possible feature, the drive means are adapted torotationally drive the filter member, the suction device or devices, orboth.

It should be noted that in the embodiment in which the filter member andthe suction device or devices are movable, separate drive means areprovided to drive the movement of each of them.

The rotational movement of the aforesaid part or parts is a particularlysimple movement to make.

According to another possible feature, the suction device or eachsuction device if therefore several of them, comprises a suction unit(for example: a pump, ejector, gravity flow, etc.) and a suction nozzle,it being possible for one suction unit (for example a pump) to be commonto several nozzles.

The suction nozzle is adapted to be positioned facing the retainingmembers and to successively sweep each of them during the relativemovement between the suction device and the filter member.

According to another possible feature, the suction nozzle is of elongategeneral shape and comprises an envelope-forming wall which, incross-section, has an open profile provided with an opening face to facewith the retaining members. For example, the opening is formed in anarcuate lip parallel and tangential to the filter surface, fastened tothe suction unit. This arcuate lip prevents the water that is suckedaway from being unfiltered water that has passed around the suction unitand not water coming from inside the

Such a shape is for example obtained from a plate of substantiallyrectangular shape bent around a cylinder in order to bring the twolongitudinal edges of the plate (the long sides) to face each other butin spaced apart relationship, to form an opening between them.

It should moreover be noted that another method for forming such asuction nozzle may consist of forming a slot in a hollow cylindricaltube, over the entire height thereof, then of slightly spreading thefree edges bounding the axial slot so formed in order to enlarge it andobtain the desired shape.

According to a possible feature, the general shape of the open profileis that of a U or a C.

Such a profile is particularly adapted to cooperate with the retainingmembers of the filter member.

According to a possible feature, in plan view, the opening has asubstantially rectangular outline of dimensions equal to or greater thanthose of the facing retaining members.

Such an opening is particularly well adapted to the configuration of theretaining members of the filter member provided with a cylindricalfiltration surface.

According to another aspect, the invention is also is directed to aninstallation comprising a channel in which water flows and a device forfiltering the stream of water in the channel, characterized in thatdevice comprises:

-   -   a frame-forming wall mounted in the channel and which comprises        a through-opening,    -   a filter member mounted on the frame-forming wall opposite the        through-opening and which comprises a filter surface projecting        relative to the wall in the upstream direction, the filter        surface having a larger area than would have a flat filter        surface fitted in the through-opening, the filter member        comprising retaining members provided face to face with the        filter surface upstream thereof in order to retain the solid        bodies that do not pass through the filter surface, or        downstream if the direction of flow of the water is from the        inside to the outside,    -   at least one suction device which is disposed opposite the        retaining members upstream thereof,    -   means for driving the filter member and/or said at least one        suction device in a relative movement between them such that        said at least one suction device is successively brought face to        face with each retaining member in order to locally generate,        through the filter member, a counter-flow of water successively        opposite each retaining member.

The filtration devices may thus be easily installed in a channel such asa sluice.

The features and advantages stated above in relation to the filtrationdevice also apply to the installation dealt with above.

According to a more specific possible configuration of the device of theinvention, the device/screen comprises a frame suitable to be connectedto a water intake and a cylindrical filter panel axially interposed in acylindrical opening of said frame, while being fastened to said frame,said cylindrical filter panel comprising a cylinder with a horizontalaxis and comprising longitudinal retaining members which are disposedupstream of the cylindrical filter panel and fastened thereto. A suctiondevice is disposed upstream of the retaining members and means fordriving the cylindrical panel and/or the suction device in a relativerotary movement are provided so as to generate locally, through thecylindrical filter panel, a counter-flow successively opposite eachretaining member, according to said relative rotary movement, tosuccessively take the debris and particles retained by them and directthem through a take-off pipe adapted to remove said debris and particlesso taken to the outside.

According to a first possible embodiment, the cylindrical filter panelis fixed whereas the drive means are adapted to rotate the cylindricalsuction device.

According to a second possible embodiment, the suction device is fixedwhereas the drive means are adapted to rotate the cylindrical filterpanel.

According to a third possible embodiment, the drive means are adapted torotate the suction device and the cylindrical filter panel.

In practice, the suction device comprises a suction pump and a suctionnozzle.

Preferably, the external volume of the cylindrical filter panel isfragmented in a circular manner into compartments by longitudinalpartitions forming the retaining members and the suction nozzlecomprises, in plan view, a rectangular outline equivalent to or somewhatgreater than one of such a compartment.

As a variant, the suction device comprises two nozzles disposedrespectively on opposite sides of the cylindrical filter panel, onedownstream in the direction of the exiting stream, the other upstream,set up in register with each other and both turned towards thecylindrical filter panel in cooperation with the relative rotarymovement and a pump whose delivery is connected to the nozzle disposeddownstream of the cylindrical filter panel.

In a configuration without fish to be saved, the take-off pipe mayfurther comprise at least one debris concentrator.

According to one embodiment, the take-off pipe comprises two debrisconcentrators and a set of valves enabling alternate use of one of theconcentrators or the other.

In a configuration with fish to save, the take-off pipe lacks anyconcentrator and the water, loaded with debris and fish, is dischargeddirectly into a pipe or channel for return to the natural environment.

In practice, the low position of the circular filter cylindersubstantially corresponds to the bottom of a sluice so equipped, whereasthe high position of the cylindrical filter panel is, if possible, atthe lower level than that of the low water level. According to anotheraspect of the invention, the screen comprises at least two cylindricalfilter panels placed one above the other in the vertical plane, betweenthe low position and the high position, each suction device beingconnected to a common or separate take-off and the driving of thecylindrical filter panels being performed by drive means that areseparate or common to both cylindrical filter panels.

According to still another embodiment, the screen is adapted to behoused instead of and in the place of a thru-flow band filter formed bya channel constituted by a bottom and two straight side walls wherevertical guides are sealed, in which the frame of the thru-flow filteris capable of sliding and a rectangular opening on the maintenance deckgenerally bordered along its upstream side by a gutter adapted toreceive detritus projected by the washing jets and a flat base of thecivil engineering construction, said screen according to the inventionbeing adapted to cooperate with the civil engineering construction ofsaid thru-flow filter.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will appear in the lightof the following detailed description and drawings in which:

FIG. 1 is a cross-section view of a water intake sluice equipped with acylindrical filter panel screen/device according to the invention,viewed from upstream;

FIG. 2 is an elevation view in horizontal cross-section on BB of FIG. 1;

FIG. 3 is a horizontal cross-section view on CC of FIG. 1;

FIG. 4 reproduces at a larger scale the details referenced D and E ofFIGS. 1 and 2; and

FIG. 5 is a horizontal view of an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As illustrated in the drawings, a filter device with a filter memberhaving a cylindrical filtration surface such as a cylindrical filterpanel screen 1 is installed in a water intake channel or sluice 2 whoseparallel masonry walls 3 and 4 each comprise, facing each other, avertical guide 5 (FIG. 3). An installation comprising the channel andthe filtration device is represented in FIGS. 1 to 3.

Such guides 5 are for example produced from metal and each form a grooveas represented in FIG. 3.

The sluice 2 is equipped with a frame-forming wall or carrier plate 6extending from one wall 3 to the other 4 and which is slid vertically inthe guides 5. The plate 6 comprises a circular opening 61 substantiallycentered on the axis 13 of the plate 6. The low part of the circularopening 61 is more generally situated very close to the bottom 14 of thesluice 2. The circular opening 61 is obstructed by a cylinder 7concentric with the opening 61 and which projects upstream relative tothe carrier plate or frame 6 (FIG. 3). The cylinder 7 is constituted byseveral spokes 8, a hub 9, and a filter member 10 fastened to theperiphery of the cylinder 7. The spokes 8 extend from the hub 9 to thecross-members 11 and are generally regularly distributed around the hub.These spokes 8 are fastened to the filter member 10. Longitudinalpartitions 12 spaced from each other delimit in pairs compartments orretaining members for the various solid bodies (detritus and particles)stopped by the cylindrical filtration surface of the filter member 10.For example, the width of the partitions 12 is several centimeters fromupstream to downstream. The partitions 12 are disposed at the peripheryof the cylinder 7 and extend radially outwardly of the filter member 10,on going away therefrom. The partitions 12 are arranged longitudinallyalong genratrices of the cylinder 7, over its entire height.

The diameter of the cylinder 7 is preferably the greatest possible, thatis to say slightly less than the width of the sluice 2, this being inorder to maximize the area of the filtration surface. The height of thecylinder may also be modified and increased if need be. However, toavoid flexing of a cylinder that is too high under the action of itsweight which, normally, would require the free end of the cylinder to besupported, it may be preferred to increase the diameter of the cylinder.

It should be noted that the water flows as indicated by the arrows inFIG. 3 from the outside to the inside of the filter cylinder beforeescaping in the downstream direction via the central opening in plate 6.

As a variant, the water flows from the inside of the filter cylinder tothe outside and the retaining members are disposed inside the filtercylinder.

The lowest water level denoted LWL is generally situated at least at theupper level of the cylinder (FIG. 1). As a variant, the level LWL may behigher or lower depending on ancillary constraints.

The hub 9 of the cylinder is provided with mechanical journals andabutments known per se. The hub 9 is carried by a shaft 15 fastened tothe plate or support wall 6 by radial arms 16.

In order to prevent water from passing from upstream to downstream ofthe filter cylinder 7 without passing via the filter member 10, theplate 6 extends at least to a level generally equal to or greater thanthe highest water level HWL not represented in the drawings.

As represented in FIG. 3, the cylinder 7 is obturated at its upstreamend 7 a which is opposite the downstream end 7 b situated face to facewith the central opening of the plate 6. The obturating wall 7 a has forexample a conical shape in this example for hydraulic reasons.

The cylinder 7, centered the hub 9, is rotationally driven by drivemeans comprising peripheral gear teeth 17, a pinion 18 and a drive motor19 (FIGS. 1, 3 and 4, detail E).

It will be noted that a lip seal 20 is for example provided between theend 7 b of the filter cylinder and the wall or plate 6.

As a variant, as shown in FIG. 5, the filter member 10 which protrudesrelative to the plate or wall 6 is conical with the base of the conesituated facing the opening of the plate or wall 6 and the point of thecone directed upstream.

A suction device is added onto the filter cylinder, comprising alongitudinal tangential nozzle 30 (FIGS. 1, 2 and 4) extending over theentire length of a generatrix of the cylinder 7. The nozzle 30 isfastened to the carrier plate 6 by one end (FIG. 2). The nozzle 30comprises a cylindrical surface open over its full height by a slot oropening 31 which is axially arranged, that is to say along thegeneratrices of said cylindrical surface and which faces towards thecylinder 7. The edges of the slot are then spread apart from each otherin order to enlarge the slot.

As represented in FIG. 1 and FIG. 4 (detail D) the cross-section of thenozzle thus formed has a U-shaped open profile the opening of which isdirected towards the retaining members of the filter member 10.

In practice, the outside volume of the cylinder 7 equipped with thefilter member 10 is fragmented in a circular manner into compartments 32by the parallel longitudinal partitions 12 forming the retainingmembers. In a plan view from the cylinder 7, the nozzle 30 has arectangular outline equivalent to or somewhat greater than once that ofsuch a compartment.

The nozzle 30 has an opening 31 oriented to face the compartments 32 ofthe cylinder, which may be equipped with flexible lips 33, 34 in orderto reduce the cross-section thereof, while enabling the occasionalpassage of bodies of greater size. The nozzle 30 is connected by a duct35 to a suction unit such as a pump 40 fastened to wall 6, for exampleon the downstream side thereof. The pipe 35 thus for example passesthrough the wall 6 and provides the fastening of the nozzle 30 thereto.

The pump 40, supplied with power for example via a cable (not shown), ischosen so as to be able to pump large items of debris and, whennecessary, of a type also capable of ensuring a very high survival ratefor fish. The water conveying debris, fish and other forms of aquaticlife is removed to its collection point by a duct 50.

As a variant, the suction device comprises two nozzles disposedrespectively on opposite sides of the cylindrical filter member orpanel, one downstream relative to the direction of the outgoing stream,the other upstream. These two nozzles are arranged in register with eachother and are each turned towards the cylindrical filter panel incooperation with the relative rotary movement and a pump whose dischargeis connected to the nozzle is disposed downstream of the cylindricalfilter panel.

According to another variant, the take-off pipe 50 comprises two debrisconcentrators (not shown) and a set of valves enabling alternate use ofone of the concentrators or the other.

In a configuration with fish to save, the take-off pipe lacks anyconcentrator and the water loaded with debris and fish is dischargeddirectly into a pipe or channel for return to the natural environment.

In FIGS. 1 to 3, an embodiment has been shown in which the suctiondevice 30, 40 is fixed, whereas the drive means 17, 18, 19 are adaptedto rotate the cylindrical filter member or panel.

As a variant (not shown), the filter member or panel is fixed whereasthe drive means are adapted to rotate the suction device.

According to another variant (not shown), the drive means areadapted/configured to rotate both the suction device or devices (ifthere are several) and the cylindrical filter panel.

The description which has just been given in particular concerning thecompartments, the suction device or devices, the relative movementbetween that device or devices and the filter member applies whateverthe form of the filter member.

However, for a filter member of non-cylindrical form the retainingmembers or compartments have different suitable shapes (for example, agenerally triangular shape for a cone), the same applying for thesuction device.

The operation of the screen is the following: when not moving, thefilter cylinder 7 is stopped, the pump 40 does not operate and the waterflows through the filter member. Debris is stopped by the filter member10 and retained in the longitudinal compartments 32 at the periphery ofthe cylinder. When it is desired to clean the filter 7, the pump 40 isstarted and the cylinder is rotated by the drive means 17, 18, 19. Thecylinder turns and the peripheral compartments 32 pass in turn in frontof the opening 31 of the nozzle 30. Each compartment is isolated fromthe general stream by the nozzle facade. The suction of the pump createsa flow in the compartment in the opposite direction to that of thenormal screening and with a speed of the same order. The debris aresucked into the nozzle 30, though the pump 40, and are removed by thepipe 50.

If a piece of debris of large size situated in a compartment 32 jams therotation of the cylinder, the drive system 17, 18, 19 stops by theeffect of a load limiter known per se and rotation in the oppositedirection is triggered, generally making it possible to get rid of thedebris causing the jamming.

The washing pump 40 and the rotary movement are stopped at the end ofthe washing cycle.

When it is required to retrieve alive the fish and other forms ofaquatic life stopped on the filter cylinder, the pump used is a suitabletype known per se. The operation is normally automatic and controlled bythe head loss generated by the filter cylinder, that is to say upon itsfouling. Devices already known in themselves ensure the safety of theinstallation.

The size of the pieces of debris to suck away is limited by the gratingof bars present in such water intake constructions. Those pieces ofdebris may then be stored while awaiting washing by virtue of thedimensions of the compartments, in particular thanks to the distancebetween the filter member surface and the free end of the longitudinalpartitions of said compartments.

It is to be noted that the filtration device or screen according to theinvention prevents any possibility of by-passing the system.

It does not generate significant turbulence in the outgoing streameither. It is thus more efficient than a dual flow band screen.

Such a device/screen according to the invention has the advantage ofbeing able to be inserted by sliding in the vertical guides cooperatingwith bearing structures for thru-flow band screens.

The filter member 10 may have mesh openings of cylindrical, rectangularor square shape or slots with respective dimensions of the order of10×10 to 0.5×0.5 mm.

The device/screen according to the invention also has an application forsluices that are inclined relative to the vertical plane.

It may even be mounted with the vertical axis and an outlet in a tunnelunder the deck.

1. An installation comprising: a channel in which water flows, a waterlevel in the channel being between a minimum water level and a maximumwater level; and a device which filters a stream of water having atleast the minimum water level in the channel, the device comprising: aframe-forming wall mounted in the channel and which comprises asubstantially-central through-opening, a filter member mounted on theframe-forming wall at the through-opening, the filter member comprisinga conical filter surface projecting relative to the wall in the upstreamdirection, the conical filter surface having a larger area than wouldhave a flat filter surface fitted in the through-opening, the filtermember comprising retaining members provided in front of the conicalfilter surface upstream thereof or downstream according to the directionof flow of the water, in order to retain solid bodies that do not passthrough the conical filter surface, the filter member being movable, anuppermost portion of the filter member being disposed at most at theminimum water level during filtration of the stream of water flowingthrough the channel, at least one suction device which is disposedopposite the retaining members upstream thereof, and a drive systemincluding peripheral gear teeth, a pinion, and a drive motor, the gearteeth extending from a peripheral end of the filter member and engagingwith the pinion, the drive motor driving the pinion which engages thegear teeth for rotationally driving the filter member in a relativemovement between the filter member and the at least one suction devicesuch that each retaining member is successively brought in front of theat least one suction device in order to locally generate, through thefilter member, a counter-flow of water successively opposite eachretaining member.
 2. The installation according to claim 1, wherein theaxis of revolution of the conical filter surface is disposedperpendicularly to the through-opening of the frame-forming wall.
 3. Theinstallation according to claim 1, wherein the retaining members aredisposed along generatrices of the conical filter surface.
 4. Theinstallation according to claim 5, wherein the retaining memberscomprise two partitions spaced apart, arranged along generatrices of theconical filter surface.
 5. The installation according to claim 1,wherein the suction device or each suction device when a plurality ofsuction devices are provided, comprises a suction unit and a suctionnozzle.
 6. The installation according to claim 5, wherein the suctionnozzle is of elongate general shape and comprises an envelope-formingwall which, in cross-section, has an open profile provided with anopening face to face with the retaining members.
 7. The installationaccording to claim 6, wherein, in plan view, the opening has asubstantially rectangular outline of dimensions equal to or greater thanthose of the facing retaining members.